Ethanol can be produced from grain-based feedstocks (e.g. corn, sorghum/milo, barley, wheat, soybeans, etc.), from sugar (e.g. from sugar cane, sugar beets, etc.), and from biomass (e.g. from cellulosic feedstocks such as switchgrass, corn cobs and stover, wood or other plant material).
Biomass comprises plant matter that can be suitable for direct use as a fuel/energy source or as a feedstock for processing into another bioproduct (e.g., a biofuel such as cellulosic ethanol) produced at a biorefinery (such as an ethanol plant). Biomass may comprise, for example, corn cobs and stover (e.g., stalks and leaves) made available during or after harvesting of the corn kernels, fiber from the corn kernel, switchgrass, farm or agricultural residue, wood chips or other wood waste, and other plant matter. In order to be used or processed, biomass will be harvested and collected from the field and transported to the location where it is to be used or processed.
In a biorefinery configured to produce ethanol from biomass, such as cellulosic feedstocks as indicated above, ethanol is produced from lignocellulosic material (e.g. cellulose and/or hemi-cellulose). The biomass is prepared so that sugars in the cellulosic material (such as glucose from the cellulose and xylose from the hemi-cellulose) can be accessed and fermented into a fermentation product that comprises ethanol (among other things). The fermentation product is then sent to the distillation system, where the ethanol is recovered by distillation and dehydration. Other bioproducts such as lignin and organic acids may also be recovered as co-products. Determination of how to more efficiently prepare and treat the biomass for production into ethanol will depend upon (among other things) the form and type or composition of the biomass.
One of the costly steps in the preparation of lignocellulosic material for fermentation is the hydrolysis of the cellulosic material, which requires the usage of enzymes in order to degrade the cellulose to sugars. Typically, large doses of enzymes are required for hydrolysis since it is believed that lignin may bind to some of the enzymes rendering them inactive. As enzymes are a significant portion of the overall cost of hydrolysis, there is an inefficiency in conventional techniques that has not been addressed.